Hach-Lange POLYMETRON 83xx User Manual

Document Number 221=183=000

POLYMETRON 83xx

2 Electrode Conductivity Probes

USER MANUAL

September 2010, Version B

Restriction of hazardous substances (RoHS)

The European Union RoHS Directive and subsequent regulations
introduced in member states and other countries limits the use of six
hazardous substances used in the manufacturing of electrical and
electronic equipment.

Currently, monitoring and control instruments do not fall within the
scope of the RoHS Directive, however Hach Lange has taken the
decision to adopt the recommendations in the Directive as the target
for all future product design and component purchasing.

Note: The following only applies to exports of this product into the
People’s Republic of China.

Plastic sensor
(8310, 8311, 8312)

Stainless steel sensor
(8314, 8394)

Digital sensor PCB O

Glass electrode O

O:

X:

O

O

2 ELECTRODES CONDUCTIVITY PROBE - INSTRUCTION MANUAL

SUMMARY

1. Overview ................................................................. 5

General.......................................................................................5

Principle of electrolytic conductivity............................................5

Influence of the temperature ......................................................6

2. Technical specifications........................................ 9

Chemical resistance.................................................................10

3. Installation and start-up....................................... 13

Cable connection......................................................................13

Programming of the transmitter................................................14

Probe calibration ......................................................................16

Probe installation......................................................................17

4. Maintenance and cleaning................................... 25

Spares parts.............................................................................27

5. Precautionary Labels........................................... 29

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2 ELECTRODES CONDUCTIVITY PROBE - INSTRUCTION MANUAL

Any use that does not comply with that described in this manual may
lead to risks for the user. Furthermore, this latter cannot change any of
the sensor or transmitter’s components. Only Hach Lange staff, or its
approved representative, is authorised to repair the system and only
components explicitly approved by the manufacturer can be used.

Any attempts to repair the instrument that go against these principles
may cause damage to the equipment or to the person performing the
repairs.

It also cancels the guarantee and may compromise the instrument’s
safety, electrical integrity or EC compliance.

Warning !

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2 ELECTRODES CONDUCTIVITY PROBE - INSTRUCTION MANUAL

1. Overview

General

The probes for which the electrochemical
exchanges take place directly between the
electrode and the solution are called
"contacting" probes or "kohlrausch" probes.
They consist of two conductor electrodes
(chemically inert in relation to the solution),
insulated from each other, in a particular and
known geometrical form (cell constant), on
which an alternating voltage is applied.
Therefore a mechanism of exchange exists at
the interface of the liquid and the electrodes
and only the use of an alternating voltage with
an optimum frequency avoids saturating the
surface of the electrodes (formation of an
insulating layer reducing the flow of current, a
phenomenon known under the term of
"polarisation").
It is the total quantity of ions present in the
solution that is measured and not the type of
ion as such.

Principle of electrolytic conductivity

Ohm’s law specifies that the current circulating
in the dipole is proportional to the difference in
potential and resistance of this dipole:

I = E / R.

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E, potential
R, resistance of the dipole such as:
the resistance of a homogenous

environment depends on the geometry of
the resitivity (characteristic of the material):

R = r. l/S where r = R/K (Ω.cm) where

C=

K

(S.cm-1)

R

K depending solely on the geometry of the
probe is (in the case of the two flat electrodes
face to face) the relation between the distance
separating the electrodes divided by their
surfaces and expressed in cm

I= E/R= C.E/K

-1

.

Influence of the temperature

The conductivity of a solution depends both on
the ionic concentration and the mobility of these
ions (size, weight, charge, viscosity). The
temperature of the solution has an influence on
these two factors (the temperature favours the
dissociation of the molecules and therefore the
ionic concentration, and increases the mobility).

In order to allow the comparison between
measurements made at different temperatures,
this measurement needs to be brought back to
a reference temperature (generally 25 °C).

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2 ELECTRODES CONDUCTIVITY PROBE - INSTRUCTION MANUAL

= C T [1 + " (T - T

C

Tref

ref

)]-1

: Conductivity compensated to the

C

Tref

reference temperature

C

: Conductivity measured at T

T

T

: Reference temperature

ref

(generally 25°C)

" : Temperature coefficient of the solution

(% / °C)

• For the sufficiently concentrated solutions
(natural waters, process…) the coefficient
is constant and is situated around 2 %.

• For slightly concentrated solutions, the
concentration of H+ protons and hydroxyl
OH- ions (stemming from the weak
dissociation of the water [H+] = [OH-] =

-7

mol/l to 25°C) can no longer be

10
neglected in the presence of the product,
this therefore leads to a non-linear
variation (compensation curve NaCI and
HCI).

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